1. Field of the Invention
The present invention relates to an aluminum solid electrolytic capacitor and a manufacturing method thereof.
2. Description of the Prior Art
A conventional solid electrolytic capacitor is manufactured by sintering fine powders (of the order of ten to one hundred micrometers) of aluminum or the like to form a column or a plate, by forming an oxide film on the surface of the sintered body by anode oxidation in an electrochemical conversion solution containing a weak acid as main component, and by forming manganese dioxide (solid electrolyte) on the oxide film by thermal decomposition of manganese nitrate. However, the solid electrolytic capacitor of this type is not of a winding type, and, therefore, it is difficult to manufacture a capacitor of a large capacitance. In order to manufacture a capacitor of a larger capacitance, the size of a capacitor is required to become larger and its cost is not profitable.
Another type of solid dry electrolytic capacitor is proposed wherein aluminum or tantalum foils forming anode and cathode of a capacitor, which have been etched and treated for electrochemical conversion, are wound to form a capacitor element with a separating paper inserted between them and manganese dioxide formed on the foils, for example, by thermal decomposition of manganese nitrate solution immersed into the element (refer to Japanese Patent Publication No. 33-5177). The impedence characteristic of the capacitor of this type is not good especially in a frequency range higher than 500 kHz and the size thereof becomes larger inevitably. This makes practical use of the capacitor of this type difficult.